Non-destructive examination of objects by means of X-ray computer tomography requires the use of high-energy X-radiation sources which allow examination of objects that have high penetration lengths or high densities. In conventional X-radiation sources, the X-ray target is a solid body; under electron beam bombardment, a high temperature increase can be observed in the interaction zone, the so-called focal spot, of the solid body, which results in high thermal loads acting on the interaction zone. A dissipation of the heat generated in the focal spot of a solid body is very difficult. The achievable output power of the X-radiation is therefore limited due to the thermal load of the X-ray target. X-radiation sources with an X-radiation of high output power are however required in particular to achieve a good image quality at a short irradiation time.
WO 02/11 499 A1 discloses an X-radiation source where a liquid jet is used as X-ray target. The liquid jet is generated by means of a nozzle and collected by a suction pipe. Between the nozzle and the suction pipe, the liquid jet is able to move freely in an evacuated chamber. The liquid jet is bombarded with an electron beam in order to generate X-radiation. The X-ray target being designed as a liquid jet allows better dissipation of heat generated in the focal spot than a solid body. The achievable output power of the X-radiation is higher than compared to X-radiation sources using a solid body as X-ray target. A drawback is that in the event of an excessive temperature increase of the liquid jet, the vapor pressure of the liquid jet may increase such that complete removal thereof is impossible, causing a part of the liquid jet to evaporate and to deposit on the internal walls of the evacuated chamber. This impairs the functionality and reliability of the X-radiation source.